Trigonometrical Survey. 6yi 



of Jupiter's first satellite, as particularly set forth in the Preface 

 to the Nautical Ephemeris of 1791. The conclusions were as 

 follows. 

 Four transits of the Moon, calculated by Mr. Wales, 



gave for the longitude - - 2o m 30 s ,6 



Two emersions of Jupiter's first satellite, calculated 



by ditto - - - - 21 14 ,5 



f Doctor Maskelyne 20 57 ,0 

 Transit of Venus, calculated by << Mr. Witchell - 2056,5 



Mr. Wales - 20 57 ,0 

 Mr. Witchell - 20 44, ,5 

 Mr. Sejour - 20 45 ,1 

 Mr. Euler - 20 sg ,0 

 Mr. Lexel - 20 51 ,0 



Sun's eclipse, calculated by -< 



Mean of the whole - 20 52 ,12 

 From the trigonometrical operations, we find the longitude 

 in time to be 20 m 44 s ,3 ; there is, therefore, a difference of 7 S ,82 

 between these different determinations : this is, probably, as 

 near as we could have expected to find it ; yet it can scarcely 

 be supposed, that of this difference, more than 2 s can be laid to 

 the account of the survey. 



In the Philosophical Transactions for 1797, p. 502, it is ob- 

 served, that angles were taken at the Lizard Light-house and 

 Naval Signal-Staff] to determine the situation of the Point it- 

 self. This Point, marked P in the diagram, makes an angle 

 of 2° 23' 16" S W, with the parallel to the meridian of St. Agnes 

 at the station on Karnbonellis, and is therefore 6g6,6 feet 

 from that meridian, and 126394 feet from the perpendicular; 



therefore 49 57' 40^,6 is the latitude 1 f , ' , p . 

 and 5 11 46 the longitude] 01 the Llzard F** 



4R 2 



